fix(rustup): update io import, Writer::write

Make it build with the latest rust-nightly (2015-01-27)

Renamed io import to old_io.
Renamed Writer::write to Writer::write_all

src/server/mod.rs

@@ -1,6 +1,6 @@
 //! HTTP Server
-use std::io::{Listener, EndOfFile, BufferedReader, BufferedWriter};
-use std::io::net::ip::{IpAddr, Port, SocketAddr};
+use std::old_io::{Listener, EndOfFile, BufferedReader, BufferedWriter};
+use std::old_io::net::ip::{IpAddr, Port, SocketAddr};
 use std::os;
 use std::sync::{Arc, TaskPool};
 use std::thread::{Builder, JoinGuard};